Negative refraction in hyperbolic hetero-bicrystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 36758086.
- Also identified by DOI 10.1126/science.adf1065.
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Abstract
We visualized negative refraction of phonon polaritons, which occurs at the interface between two natural crystals. The polaritons-hybrids of infrared photons and lattice vibrations-form collimated rays that display negative refraction when passing through a planar interface between the two hyperbolic van der Waals materials: molybdenum oxide (MoO<sub>3</sub>) and isotopically pure hexagonal boron nitride (h<sup>11</sup>BN). At a special frequency ω<sub>0</sub>, these rays can circulate along closed diamond-shaped trajectories. We have shown that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps that result from polaritonic-level repulsion and strong coupling.